In a manufacturing process for electronic devices, such as semiconductor devices, liquid crystal display devices, and organic electro-luminescent (EL) elements, a film forming process is performed to form a conductive film or an insulating film on the surface of a substrate. A plasma-assisted film forming process for forming a film on a substrate using plasma is often employed in this film forming process, for example for depositing interlayer dielectrics (ILDs) for integrated circuits.
Fluorocarbon (CF) films are promising materials for use as low-dielectric constant (low-k) ILDs and other applications. A problem that is commonly encountered when integrating a CF film with other materials is that the contact between the CF film and the other materials thermally deteriorates during further processing. The further processing can include annealing of a copper wiring layer formed in recessed features of the ILDs. The cause of the thermal deterioration is thought to be a decomposition reaction in the CF film due to the presence of dangling bonds in the CF film. The dangling bonds include unsaturated carbon bonds that lack fluorine atoms. The thermal deterioration results in fluorine diffusion and can lead to reduced adhesion between the CF film and the other materials in the integrated circuit. Eventually, the reduced adhesion can lead to film corrosion and film peeling that may be observed as film blistering on the substrate.
However, it is difficult to prepare high quality CF films by plasma processing, as well as CF films that have low concentration of dangling bonds and good thermal stability. Increasing the thermal stability of the CF films prevents or reduces the fluorine atom diffusion and improves adhesion between the CF films and the other materials in contact with the CF films. Attempts to reduce the amount of fluorine on the surface of the CF film have included performing a thermal treatment of the CF film before depositing other material layers on the CF film, or depositing a titanium metal on the CF film due to the relatively good adhesion properties at the interface of these two materials. However, these attempts have not yielded manufacturable solutions and new methods are needed for depositing CF films having a low concentration of dangling bonds and good thermal stability.